没读明白
问题描述：
没读明白
A list of numbers has a mean of 8 and a standard deviation of 2.5.If x is a number in the list that is 2 standard deviation above the mean,what is the value of 单词没问题但题没看懂,
答
平均值=8
方差=2.5
x是平均值+2个方差
x=8+2*2.5=13